# semalock
[](https://crates.io/crates/semalock)
[](https://crates.io/crates/semalock)
[](https://travis-ci.org/longshorej/semalock)
semalock is a Rust library for controlling concurrent access to files on POSIX operating systems in an efficient manner.
It uses a combination of POSIX named semaphores and exclusive file locks to safely and efficiently acquire exclusive access to a file. This has been observed to be particularly efficient on Linux, with under 5% of CPU time spent on lock overhead with 8192 processes.
# Usage
The following shows usage of semalock. This program opens `/some/file` and appends some text to it. Try it with GNU parallel to measure performance amongst multiple competing processes.
```rust
// Acquire and open a file and semaphore
let mut lock = Semalock::new(Path::new("/some/file"));
// Do some stuff to the file
.seek(SeekFrom::End())
.and_then(|_| lock.file.write(b"hello world\n"))
});
```
# Supported Operating Systems
The following operating systems have been tested:
* GNU/Linux 4.16
The following operating systems have not been tested but should work:
* FreeBSD
* GNU/Linux 2.6+
* macOS 10.4+
* NetBSD
* OpenBSD
Supported operating systems must support provide the following:
* flock
* sem_get_value
* sem_open
* sem_post
* sem_timedwait
* sem_unlink
The following will not work:
* Windows NT
# Development
You'll need Cargo. More notes to come at a later date.
## Releasing
1) Upgrade version in `Cargo.toml`
2) Commit changes
3) Create and push a tag: ```git tag v<version>; git push v<version>```
4) Release on crates.io: ```cargo publish```
# Author
Jason Longshore <hello@jasonlongshore.com>